Standalone Exchange Online Plan license supported in Exchange Hybrid?

Yes the Standalone Exchange Online Plan license does support Exchange Hybrid deployments, you can see this also confirmed https://social.technet.microsoft.com/Forums/en-US/18eaac4b-1242-4dac-879e-d8702f701efd/exchange-online-plan-1-hybrid-deployment?forum=onlineservicesexchange. 

Here are the https://technet.microsoft.com/en-us/library/exchange-online-service-description.aspx that support hybrid, as discussed https://answers.microsoft.com/en-us/msoffice/forum/msoffice_o365admin-mso_dep365/exchange-hybrid-with-office-365-business-plans/80c97b0d-1a57-4db2-9f81-505b29c4bd2b and that does include Office 365 Business Essentials/Premium in theory but has a caveat of requiring extra licencing, as explained in the link.